Applying camera track to external clips
If you simply want it to follow one of the tracks, what you're looking for is the 'Track Position' node (in the Input section of the compositor node list).  Just give it the video clip and a track that's the same depth as the effect you're adding.  Excuse the lack of actual files in this example, but in the compositor, create the following (vector blur is optional):



You may need to add another transform node to just the EXR sequence so it lines up correctly.

Just to cover my bases, if you need a more 3D layering, you'll add the sequence to the Blender scene projected onto a mesh, plane or otherwise.  To include alpha as part of the plane, you just need to use the alpha as a factor of a mix shader: